The jet fuel supply system of high-traffic commercial civil airports generally comprises an underground fuel distribution piping system that transports fuel to the fuel valves which are distributed around the airport terminals for facilitating fueling of the arriving and departing aircraft in a timely manner. At high-traffic airports, the aircraft fueling operation may also be performed through mobile dispensers (e.g., fuel trucks) that bring the fuel to the aircraft and pump it at the required aircraft inlet pressure, provide additional fuel filtration, as well as provide flow measurements for ticketing and accounting purposes.
In these types of high traffic airports, the underground jet fuel piping system is equipped with underground jet fuel valves which are installed inside underground valve pits that are often positioned near the terminal gates where the aircraft undergo fueling operations. Additionally, valve vents are provided to degas the piping during piping system start-up and for overpressure control purposes. The valve vents are installed in vent pits which are dispersed at predetermined locations along the main pipeline including proximate to the terminal gates.
Referring to FIG. 1, a prior art jet fuel hydrant pit assembly 100 is illustratively shown. The pit assembly 100 is formed below ground level in the apron 102 and can be prefabricated with fiberglass or steel walls 104 that is cylindrical or rectangular in shape. The pit assembly 100 includes a protective cover 106 that is rotatably or pivotally hinged for access, and in the closed position is substantially flush with the apron 102 for protection and safety purposes. The cover is opened to provide access to the jet fuel valves during refueling and maintenance operations. The pit assembly 100 is positioned in the vicinity of the main fuel pipeline 108 and a lateral connecting pipe 110 is attached at one end to the fuel main 108 and with the opposite end extending into the pit assembly 100. A manual maintenance valve 112 is mounted on the discharge end of the lateral connecting pipe to shut off the flow of jet fuel therethrough. A hydrant valve 114 is mounted via a pipe fitting over the maintenance valve and is configured to receive a fluid-tight end fitting from a fueling hose (not shown). During operation, the jet fuel is pumped from a central pump station through the main fuel pipeline, the lateral pipe connection, the hydrant valve, and into a fueling hose releasably coupled to the hydrant valve to fill the fuel tanks of an aircraft or mobile fuel dispenser.
The jet fuel system further includes surge absorbers to avoid overpressure peaks that may occur during aircraft fueling. The system pressure is maintained by a pressurization control system that includes one or more pressure sensors (normally located near the main fuel pump facility), and a series of jockey pumps and circulation pumps that maintain the fuel pressure during fueling operations. Fuel leaks in the underground fuel systems can be caused by external corrosion to the piping which can develop gradually over time, as well as poor weld or gasket seals between the piping, fittings, and the like. The presence of hydraulic noise and surges generated by frequent aircraft refueling and the combined actions of the pressure recovery jockey pumps and the circulation pumps, which maintain the necessary jet fuel pressure during fueling operations, often makes it difficult to detect and locate existing underground leaks in real time. In the event an underground leak occurs, the continued operation of the jockey and circulation pumps often masks pressure losses created by the fuel leak.
There are numerous airports that have jet fuel pipeline systems which are not equipped with instrumentation for taking continuous pressure measurements at specific tapping or test points along the underground piping system. Installing additional pressure tapping (i.e., test) points and the associated electrical conduits for providing power to the instrumentation is often prohibitively expensive, due to high construction costs for demolishing and then replacing the thick concrete flooring structures (e.g., the aprons) that surround the terminals, taxiways and tug roads.
Accordingly, current pressure detection practices in the jet fuel line under the airport apron require taking the measurements manually at a few specific locations by first turning off the jockey and circulation pumps and then conducting a visual inspection of the vent and jet fuel valve pits. Namely, prior art pipeline leakage detection systems typically employ leakage detection tests, such as hydrostatic testing and depressurization monitoring, which are conducted manually. These manual detection techniques subsequently require subjective decisions to be made from data measurements that are collected at different times, and which must then be analyzed without having the benefit of sufficient data synchronization.
Similarly, there is no measurement mechanism for continuous measurement and retransmission of jet fuel pipe-to-soil potentials from vent-valve pits installed remotely around airport aprons to a central processing station. Accordingly, the prior art pipeline leak detection systems lack sufficient capabilities to simultaneously record and verify the pressure variations due to underground leakage with the corresponding changes in pipe-to-soil potential.
Moreover, there is no wireless communication system, such as a solar-powered wireless communication system available for jet fuel pipes installed (i.e., buried) beneath an airport apron that can collect, time stamp and retransmit continuous real-time measurements of both pipe-to-soil potential and pressure to a central control station for further processing. Accordingly, the detection and location of underground leaks is accomplished by methods that do not have real-time synchronization of measurements. Consequently the prior art systems lack of the necessary means to recognize actual leakages already manifested in the soil from pressure transients that are present in daily operations of airport jet-fuel lines.
In addition to jet fuel pipeline pressure monitoring, jet fuel piping systems are also generally protected by impressed current cathodic protection (ICCP) systems, which utilize a transformer and DC (direct current) rectifier that applies an electrical current to the piping structure to protect it from external corrosion. The impressed current cathodic protection systems typically include pipe-to-soil potential measurement points which are used to monitor the effectiveness of the cathodic protection. However, similar to the lack of pressure instrumentation for continuously monitoring pressure leaks at specific locations, there is no instrumentation available at specific locations (e.g., valve and vent pit assemblies) along the jet fuel piping system that enables continuous monitoring of pipe-to-soil potential measurements.